Excitation-emission cycle scenarios

The procedure that we propose to enhance the concentration of a particulap enantiomer when starting with a racemic mixture, that is, to purify the mixture) is as follows [259], The mixture of statistical (racemic) mixture of L and irradiated with a specific sequence of three coherent laser pulses, as described below. These pulses excite a coherent superposition of symmetric and antisymmetric vibrational states of G. After each pulse the excited system is allowed to relax bg t to the ground electronic state by spontaneous emission or by any other nonradiativ process. By allowing the system to go through many irradiation and relaxatio cycles, we show below that the concentration of the selected enantiomer L or can be enhanced, depending on tire laser characteristics. We call this scenario lat distillation of chiral enantiomers. 

Fig. 19 A, B and C correspond to the excitation sequences described in Fig. 18b. (a) The excitation cycle monitored from reflected excitation light of both lasers. The fluorescence time traces (b, c) match the excitation cycle depicted in (a), (b) Fluorescence time trace of a single TDI molecule, (c) Section of an experimental time trace of 1. The emission at the TDI channel (red) showed a strong dependence on the excitation scenario. During pulse sequence C, the intensity decreased significantly compared to scenario B because of efficient SSA. The PDI channel (green, magnified 10 times) detected no fluorescence at any time. At 9.1 s the donm chromophore (PDI) underwent photobleaching. Consequently, an emission pattern similar to that of single TDI molecules (c.f. b) was observed...

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